In today's military world of explosive ordnance, the state of the art technology is to be able to have an initial explosive charge mechanism that will first explode upon impact to start to make an opening before the primary explosive charge goes off. This may be followed by the solid bullet body or a second explosive charge. The state of the art applies primarily to large cannon artillery shells and very little of such technology applies to firearm cartridges.
A pre-explosive charge which may be followed by a larger explosion enable ordnance to penetrate farther and deeper into an armored target. Even though this first and second stage explosive ordinance works well, the military has few options to choose from in this area. The primary reason for this is because this type of ordinance will not fit in or work safely in the majority of the available military weapons.
Explosive projectiles will usually include a high density, sub-caliber penetrator totally enclosed within in a hardened, high-explosive-filled tubular steel body. A nose incendiary within the tubular steel body is ignitable by impact with a target to in turn ignite a second explosive after a suitable time delay. Because all of the penetrator components are housed within a single steel casing, care must be taken to ensure that the incendiary is arranged so that it does not prematurely activate the high-explosive charge. Two charges with a single casing delivered to the target are integral to the existing art.
When impinging a light target, for instance an airplane fuselage, the nose of the traditional projectile will be compacted and the ignition charge will be ignited. Before the second charge in the penetration element explodes the entire projectile will, typically, have pierced to the inside of the target and then after this delay will explode and splinter or fragment the penetration element as well as the casing. Thus, the design typically involves a single ballistic casing encapsulating two explosive charges and a penetrator, rather than a single explosive charge outside the ballistic casing and in its own container followed by a penetrator.
If a sub-caliber penetrator is included, the prior art typically has it enclosed within the tubular steel body of a full-caliber projectile. An outer coating of copper or aluminum is often used so that the hardened heavy metal tube or core of the projectile has a smaller caliber than the weapon, but the coating of the projectile engages with the rifling of the barrel.
Duplex projectiles have been described. A duplex projectile is fired from a gun bore and in one such instance has a tubular projectile and a conically-shaped projectile fastened within the tubular projectile. The conically-shaped projectile is released from the rear of the tubular projectile once the two exit from the bore. While in the barrel, the conically-shaped projectile blocks the release of gas pressure from the cartridge while the round is under pressure from gun propellant gases and also serves as a sub-caliber projectile once it and the tubular projectile leave the muzzle and separate. The tubular projectile or the conically-shaped projectile may be filled with an explosive. Conventional cartridges are not used for this art and the two projectiles are not physically linked together once they leave the barrel.